July 4, 1944.
G. s. ALLIN
2,352,593
_ WHEEL EQUIPPED TRACTOR
Filed Oct. 20, 1941
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4 Sheets-‘Sheet 1
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INVENTOR
GEO/96E J ?LL/N
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ATTORNEY
July 4, 1944.
2,352,593
,6. S. ALL-IN
WHEEL EQUIPPED TRACTOR
Filed Oct. 20, 1941
k»g.
4 Sheets-Sheet 2
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‘
‘
INVENTOR
6627/9615 J?LL/n
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'
ATTORNEYS
July 4, 1944*»
G. s. ALLIN
2,352,593
WHEEL EQUIPPED TRACTOR
Filed 001;. 20, 1941
4 Sheets-Sheet 3
3“.
‘R.
“a
.
INYENTOR
650,965 .5 HAL/N
.
BY
ATTORNEY
July 4, 1944.
‘
<;_ s_ ALUN
2,352,593
WHEEL EQUIPPEDv TRACTOR
Filed Oct. 20, 1941
4 Sheets-Sheet 4
INVENTOR
WWI)
ATTORNEY
Patented July 4, 1944
v 2,352,593
umreo s'rArEs PATENT orrica
2,352,593
WHEEL EQUIPPED TRACTOR
George S. Allin, Seattle, Wash, assignor to
Isaacson Iron' Works, Seattle, Walla, a corpo
ration of Washington
Application October 20, 1941, Serial No. 415,705
5 Claims. (Cl. 180-17)
Braking of the vehicle is rarely employed except
This invention relates to tractors, and has ref
to aid in steering control, and this is accom
plished through the braking facilities incor
porated in, or in connection with the steering
erence more particularly to improvements in
wheel equipped crawler track replacement units
of those kinds which have been described and
, illustrated in my copending applications, filed
clutches.
dated Feb. 9, 1943), and 398,873 (Pat. No. 2,311,
922 dated Feb. 23, 1943).
In connection with the aims and purposes -of
the present improvements, it will be here ex
plained that the inventions that have been de
scribed, illustrated and claimed in the above
numbered applications relate to the design, ap
plication and use of novel types of wheel equipped
units as replacements for the crawler tracks of
‘well known and universally used tractors, such
for example, those known by the trade names
“Cle-Track,” “Caterpillar," “International" and
“Allis-Chalmers"; such replacements being de
signed to convert the tractors to which they are
applied from the crawler types to wheeled types,
with incident advantages of higher speed and
greater utility, but without loss of maneuver
ability or e?iciency.
As is well known in the art, tractors of those
kinds above identi?ed by their trade names, are
now equipped with crawler track mounting
frames at opposite sides of the tractor main
frame. These track frames extend lengthwise of
the main frame and are equipped with sprocket
wheels, and suitable guides for mounting the
crawler tracks thereon.
The crawler tracks at opposite sides of the
tractor are independently driven through certain
of their mounting sprockets and each may be
controlled independently of the other to provide
for steering the tractor.
.
In those kinds of crawler type tractors to which
the present replacement units are made ap
plicable according to the disclosures of the pre
“
-
vantages 'to be gained by use of such replace
ment equipment, su?ice it to say that in actual
‘test, they have surpassed all expectations in
many uses and under varying conditions.
[5
It has vbeen disclosed, however, that because
of the relatively high speeds made possible and
at which the tractors are normally operated when
equipped with the present wheeled units, the
braking facilities as originally provided in con
'
20 nection with the power transmission and steer;
ing clutches is entirely inadequate, and conse
quently is relatively short-lived. This will be
readily understood when it is remembered that
ordinarily, tractors of the mentioned crawler
25 types operate at speeds of from three. to six
miles per hour, whereas, with the present wheeled
equipment, they are operated at speeds of from
ten to twenty-five miles per hour. Thus, it is
imperative to safety, adequate-control and satis
30 factory operation that positive, more durable
and more adequate braking equipment be pro
vided than is available in the original equip
ment. Furthermore, it is believed to be most
practical that the additional braking facilities
35 should be applied directly to the ground wheels
and not merely addedto the already existing
brakes of ‘the steering clutches.
In view of the above, it has been the principal
objects of this invention, ?rst, to improve the
40 braking facilities oi’ tractors that have been
equipped with track replacement units of the
kind disclosed in my copending applications
or straight rearward travel is accomplished by
the forward or rearward driving of the tracks is
in unison, while turning and pivoting is effected
through the differential driving of the individual
crawler tracks. The ‘differential driving is ac
complished through mechanism referred to in the
art as "steering clutches”; there being such a' 50
clutch provided in connection with each crawler
track, and these clutches and their corresponding
brakes are individually controllable from the
tion of brake pedals and clutch control levers.
..
and without reciting the various uses and ad
viously mentioned applications, straight ahead I
driver's position through the proper manipula
‘
Without going into any lengthy description of
details of the various crawler track replacement
units which have been illustrated and described
in .the above mentioned pending applications,
under Serial Nos. 337,647 (Pat. No. 2,265,986
dated Dec. 16, 1941); 375,279 (Pat. No. 2,284,790
dated June 2, 1942); 385,261 (Pat. No. 2,310,727
above mentioned; second, to apply braking
equipment directly to the track replacement
units, and, third, to so associate the additional _,
braking means of the wheeled units with that
already existing in connection with the steering
clutches and power transmission facilities of the
tractor that, in the conversion of the tractor
from the crawler to the wheeled type, the orig
inal steering clutch braking facilities supple
ment those of the replacement units, particu
larly in their use as emergency brakes.
Still another object oi’ this invention is to pro
vide an improved means for the vertical guid
2
2,302,003
ance of the oscillating ends of the frames of the
and substantially formed, rearwardly disposed
wheeled units whereby to relieve the pivot axle
housing I, which encloses the power transmis
of twisting and lateral strains and to insure a
sion gearing the two steering clutches and their
more substantial and better construction, par
brake mechanisms for the crawler tracks. As
ticularly where heavy units of large size are con
shown in Fig. 2, this housing is rigidly fixed to
cemed.
a forwardly extending frame structure compris
Still other objects of the invention reside in the
ing spaced, opposite side beams, 2, between which
details of construction of parts, in their combi
the engine, or prime mover 3 is supported. Ex
nation and mode of operation, as will hereinafter
tending horizontally through the housing I is a
10 supporting shaft 4, of substantial diameter, which
be fully described.
In accomplishing these and other objects of
has its opposite end portions, designated by ref
the invention, I have provided the improved
erence character 4a, extended through and be
details of construction, the preferred forms of
yond the opposite side walls of the housing.
which are illustrated in the accompanying draw
These extended portions of the shaft originally
ings, wherein
were intended to serve as pivot axles for mount
Fig. 1 is a side view of a tractor equiped with
ing the track frames and also as mounting axles
wheeled track replacement units embodying the
for the track driving sprocket wheels. This axle,
braking facilities and other features of the pres
in the art, is generally referred to as the "pivot
ent invention.
-
axle."
Fig. 2 is a plan view of a portion of- the trac
‘
Disposed transversely of the frame structure 2,
substantially forwardly of the pivot axle 4, is
a laminated spring 5. This spring is functionally
tor, showing the track replacement unit at one
side in horizontal sections, and illustrating the
tractor driving mechanism, including the steer
mounted medial of its ends in a support that is
ing clutch and brake mechanism associated with
plane parallel to the tractor frame and Just with
pivoted in the frame structure 2. This spring
is known as the equalizer spring. Opposite end
portions of the spring 5 extend below and equally
beyond the opposite side beams 2 of the main
in the set of wheels at one side as on the line
frame structure, and, in their normal use, en
that unit.
,
'
Fig. 3 is a sectional view taken in a vertical
3-3 in Fig. 4, showing the braking facilities and
gage with the vertically oscillating ends of the
crawler track frames to support and ‘cushion the
forward portion of the tractor frame.
With this usual arrangement of parts, the
its control mechanism for that set of wheels.
Fig. 4 is a plan view of the same parts.
Fig. 5 is an enlarged, cross sectional view on
the line 5-5 in Fig. 2.
main tractor frame is supported through the
_
Fig. 6 is a section, taken on the line 6—% in Fig.
mediacy of cross shaft 4 and spring 5, and it is
to these parts that the present wheeled units are
applied to support the main frame in a like man
ner both for propulsion and steering.
5, showing the brake shoes and their actuating
cam and lever.
Fig. 7 is an enlarged, cross section on line 7-4
in Fig. 3.
Fig. 8 is a perspective view of the present swing
frame.
-
The original equipment of the tractor, besides
the prime mover or engine 3, includes the drive
40 shaft 6 that extends rearwardly from the engine
Fig. 9 is a side view or elevation of the braking
and is operatlvely connected, by suitable gearing
devices as applied to the unit, in. Fig. 8.
Fig. 10 is a diagrammatic layout of the vacuum
as shown at 1 in Fig. 2, with a short, transversely
supported shaft 8 which, at its ends, is operatively
connected through the steering clutch mech
anisms, each of which is designated in its entirety
by reference numerals 9, with pinion gears 10.
The gears l8 drive relatively large gear wheels
ii that are mounted to revolve upon the extended
end portions 4a of the pivot axle Q at opposite
sides of the main frame.
For purpose of better understanding, it will be
connection and control valve at one side of the
tractor.
‘
Fig. 11 is a cross sectional detail of the vac
uum applying valve mechanism. as used with each
wheeled unit.
Referring more in detail to the drawings
It is to ‘be understood that while the crawler
track replacement equipment that is herein illus
trated is of such design and detail as to adapt
it to a. tractor of a particular kind, namely, the
explained that each of the steering clutch mech
anisms 9 embodies a clutch C and a brake B, to
which latter a brake band b is applied. The
“International” tractor, it is quite evident that
by slight modi?cation in detail, and without de 55 clutches 9, associated with brake mechanisms
at opposite sides of the tractor, are intended to
parting from the spirit of the invention that is
be individually controlled by the vehicle driver
herein set forth, the unit could readily be made
through the manipulation of hand levers C1.
applicable to other kinds or makes of tractors of
this general type, known as “crawlers."
Likewise, the brakes are individually controlled
In the present drawings and in the following 60 by manipulation of foot pedals B1.
description, only such parts as are directly con
cerned with the present invention have been
shown in detail, or will be speci?cally referred
In Fig. 3, I have shown the lever C1 for the
mechanism at the near side of the tractor as
being pivotally supported at its lower end by pivot
S, and operatively connected to a rearwardly ex
tending rod 1- which, in turn, is connected to a
lever arm t, ?xed on a rotatable, vertical pivot
shaft 1). The shaft p has another lever arm d
?xed thereto and this arm, in turn, has opera
tive connection, as at e in Fig. 4, with the con
In the general construction of any one of those
crawler type tractors which I have in mind in 70 trol device of corresponding clutch C. By for
connection with use of the present improved
ward movement of the lever C1, the clutch C will
be released against the holding pressure of a
equipment, there is a main frame structure which
mounts the engine, or the prime mover, and the
spring. not shown, as is well understood in the
. various tractor controls. The main frame. struc
art.
to; the gist of the invention residing in the pro
vision of braking equipment for crawler track
replacement units employing large, rubber tired
wheels, and used in addition to and supplemented
by the original steering clutches and their‘ brakes.
ture, in a typical construction, includes a closed 75
The brake that is associated with the clutch C
3
2,852,598
comprises the drum to which brake band b is
applied. The band b has an end connection,
designated at w in Fig. 3, with a pivoted bell
crank arrangement I which in turn has an op
erative connection, later described in detail, with
the foot pedal B1 through which pressure on the
pedal operates to tighten the band I) to apply
braking pressure to the drum. Spring means,
not shown, operates to release the brake when the
Formed through the forward end portion of,
the arm 2|a is a socket, or seat 43 within which
an end portion of the equalizer spring 5 engages
to yieidingly support the forward end of the ve
_ hicle. Also ?xed rigidly to the forward end por
tion of the bracket arm 2|a is a guide 46 formed
with a vertically extending slot 41 wherein the
two vertically spaced rollers 48-48, carried by
'
a bracket v49 that is rigidly bolted to the adjacent
side beam 2 of the main frame, are contained to
The present crawler track replacement equip
ment embodied by the invention includes, for
or ‘inward displacement relative to the main
pressure on .the foot pedal is removed.
guide and hold the swing frame against outward
each side of the tractor, a pair of ground wheels
frame, but without interfering with its intended
arranged in tandem, preferably of substantial
oscillating action in a vertical direction. The
. slot 41 in this case is substantially longer than
the distance of vertical spacing of the rollers so
as not to interfere with the action.
The rear ground wheel i5 of each set is mount
ed to rotate freely on the extended end portion .
- diameter and equipped with heavy duty pneu
matic tires._ Each- set of wheels is mounted by
a swing frame structure and the wheels are of
equal diameter and are disposed quite close to
gether.
In the present construction, the rear
wheel l5 at each side of the tractor is adapted ‘
' to be directly driven from the engine through
the corresponding steering clutch mechanism, as
will presently be' explained, and the front wheel,‘
i6, is driven in unison with the rear wheel by a
sprocket chain belt connection as later described.
Each of the swing frames comprises, as seen
in Fig. 8, a horizontally disposed, longitudinal
beam 20, forming the outside member, an angle
‘bracket 2| ?xed to the beam 20, and a brace
4a of pivot shaft 4.
Each wheel i5, as shown,
is of the same size and character of construction
of the front wheel iii. The rear wheel comprises
a body disk 50 that is bolted to the outer end
?ange 5| of a hub member 52 revoluble about the
shaft end 4a. The hub member, in turn, is ?xed
at its inner end coaxially to the corresponding
gear ii to turn therewith. The body disk 50
carries a tire mounting rim 56 and this mounts
a pneumatic tire 51.
'
.
As noted best in Fig. 2', the body disks of the
two wheels are formed with outwardly extending
member 22 ?xed to the bracket. The longitu- 1
. dinal beams 20 of the swing frames at the oppo
site sides of the main frame are operatively ?xed
hub-like portions 58, and applied thereto, and
at their rearward ends to pivot bearings i9
mounted on the outer ends of the pivot axle d.
keyed thereon, as- at 59 in Fig. 5, are sprocket
wheels 60 about which, for each tandem set of
The beams 20 are adapted to oscillate ‘freely ‘
at their forward ends in vertical planes, and the
angle brackets 2| are ?xed to the beams 28 to
oscillate therewith. Each bracket 2| comprises
wheels, a chain belt 12 operates as a means of
causing the wheels to rotate in unison, both be
ing- positively driven and rendered eilective for
traction in driving or in braking.
The gist of the present invention resides in
and held rigidly parallel to the swinging end of 40 the provision of more adequate and more effec
tive braking facilities than is possible to obtain
the beam 20 by a bracket leg 2|b that is disposed
through the original steering clutch brakes. It
at a right angle to the leg portion Zia, and at its
will be observed in Figs. 2 and 5, that the front
outer end is rigidly secured by suitable means to
wheel hub has a brake drum 15 bolted thereto'at
the beam 20 at approximately its medial point
its inner end, and that internally of the drum, 9..
passing between the tandem wheels i5 and it.
pair of expanding brake shoes ‘i6 are operatively
In the present showing, the beam 20 is of channel
located. These shoes are pivotally supported at
form, while the leg 2 la of the bracket 2| is fabri~
a horizontal leg 2|a that is spaced inwardly from ’
cated from two angle irons placed edge to edge
their lower ends, as noted in Fig. 6, by pivot bolts
‘i1 mounted in ,a bracket 18 that is ?xed about
outer end, the arm 2|a has a solid casting ?tted 50 the inner end portion of the spindle 35. At their
upper or swinging ends, the brake shoes are
and secured therein and provided for mounting
formed with opposed cam rollers 80 between
the equalizer spring, as later described.
which a cam 8| is located. The cam 8| is ?xed
The leg 2|a terminates at its forward end ap
on a cam shaft 82 rotatably mounted in alined
proximately even with the forward end of the
bearings 83-83’. on the bracket 18 and arm 2|
beam 20 and mounts a spindle 35 on which the
of the swing frame structure, and adapted to be
forward ground wheel iii of the unit is revolubly
rotatably actuated to effect rotation of the cam
mounted. The wheel i6 has a hub portion 3'!
and the expanding of the shoes against the drum.
_ revoluble on the spindle and the hub is equipped
A coiled spring 88 connecting at its ends to the
with an outer end flange 38 that mounts a wheel I
body disk 39, equipped with a rim 40 carrying a 60 oscillating ends of the brake shoes, operates to
to form a hollow tube, as notedin Fig. 7. At its
pneumatic tire 4i; these parts being best shown
draw them toward each other to disengage the
in Fig. 5. The outer end of the spindle extends
through a hole 42 in the forward end of the
beam 20, and is ‘secured by the application of a
nut 44 to a threaded outer endportion of the
drum and release the braking action. The cam
shaft 82 is equipped with a vertically extending
spindle.
.
To give lateral rigidity to the swing frame
structure, the brace bar 22 is ?xed solidly to the
rearward end portion of the bracket 2| as by the
lever arm “to which a connecting rod 97 is at
tached. The rod 91 extends rearwardly to a
"vacuum booster" cylinder designated in its en
tirety by reference numeral Hill. This booster
comprises an air-tight drum, iiii, ?xedly mount
ed on the swing frame bracket 2| by a support
bolts 45, and extends therefrom in an inwardly 70 IN’. The drum is divided by a flexible dia
phragm I02 to which the end of rod 91 is ?xed.
and rearwardly curved direction, and at its end
It will be understood that if vacuum is applied
is pivotally mounted on the pivot axle 4 at a
point close to the longitudinal axial center of.
to the drum at one side of the diaphragm, the
diaphragm will be de?ected accordingly, and thus
the tractor, as will be understood by reference
to Figs. 2 and 4.
25 a pull can be exerted on the rod 91 toapply the
4
2,852,598
The valve mechanism contained in housing I21
brakes in accordance with the extent of vacuum
is such that upon seating of the valve I35, the
It is to be understood also that the braking
vacuum in the chamber I3I will be broken to per
facilities at opposite sides of the tractor are alike,
mit release of the brake. This might be accomboth in construction and mode of operation, and
plished in various ways; for example, through a
that the equipment illustrated in Figs. 3 and 4.
.passage I36a in the‘rod I36 which becomes closed
which controls the braking mechanisms at the
when rod I26 is moved to unseat the valve I35.
near side, would be duplicated at the opposite
and a port I3 la: in the inside wall of chamber I3I.
side.
By means of the facilities described, it is pos
In the arrangement of parts illustrated in Figs. 10 sible to effectively and properly control the brak
2 and 3, it will be observed that the brake pedal
ing of the vehicle for all ordinary operations
BI is pivotally mounted at its lower end, and that
through the wheeled units. This braking may
a connecting rod I05 extends rearwardly from an
accomplish the quick stopping as well as the
operative connection with the pedal, and this
steering of the vehicle and is all that is ‘required
operates through connections indicated at I in
for normal operations. However, the steering
Fig. 3, to control the braking‘ of the steering
clutch brakes are always available and can be
clutch mechanism 9.
used for unusual situations as emergency brakes.
The connection between the foot pedal and
‘In Fig. 9, I have illustrated the application of
clutch, besides the rod I05, includes a valve hous
brakes for both wheels of each unit. In such
ing I21 and a rod I26 that extends from the hous
cases of use, two booster drums I00—,I00' are em
ing to the lever I, later more fully described.
' ployed at each side of the tractor, and each wheel
In the present improved arrangement of brak
is equipped with brake drum and shoes corre
ing facilities, a vacuum tank I25 is mounted on
sponding to those shown in Fig. 5. vFrom the
the tractor at any suitable location ‘and vacuum
drums, rods 95 and 95a extend to the cam levers
is drawn and maintained therein by a pump, not .
96 of the front and rear wheels respectively, and
shown. This pump might well be operated
conduits lead from the valve housing at that side
applied.
’
through a connection with the engine 3. A vac
to both booster drums. Thus, when an applica
uum connection, including a ?exible conduit I26
tion of braking force is made, it opens the vacuum‘
leads from the tank' I25 to the control valve
housing I21 that is interposed in the braking con 30 valve to admit vacuum to both ‘drums in like,
amount.
.
.
nection between foot pedal B1 and lever f, and
As
a
detail
of
this
construction,
each
unit
is
from this housing I21, a ?exible conduit I29
equipped with a sprocket chain tightening
leads to the drum of vacuum booster I00.
'
means, as shown best in Fig. 1. Each tightener
Now referring to the enlarged cross sectional
view of the valve housing I21, as shown in Fig.
11, it will be observed that the vacuum line- I26
comprises a plate I50 disposed vertically along
the side of the upper run of thewhain belt 12,
ing passage normally closed by a valve I35 on a .
ward direction. A coiled spring I31 surrounds
top edge of the plate is connected by a link I53
with a bracket I59 that is fixed to the beam 20,.
and the link is equipped with adjusting nuts as
the rod within the housing and bears against the ,
valve to yieldingly hold it seated.
»
as required to place more or less tension on the
pivotally mounted at its lower edge by bolt I5I in ,
opens to a chamber I30 in the housing, and that
a bracket I52 carried byvbeam 20. On the plate,
the chamber I30is surrounded by a chamber I3I
sprocket wheels I54 and I55 are mounted to en
with a lateral outlet I32 from which the conduit
I23 leads to the booster cylinder I00. The 40 gage with the chain belt at top and lower sides
.and at an interval spaced along the ‘belt. The
chambers I30 and I3I have an intercommunicat
rod I36 that extends from the housing in a for-'
at I60 whereby. its effective length may be varied I "
belt.
‘._
.
The housing I21 has a socket I40 at one end
Having thusdescribed myvinvention, what I
within which one-end of the rod I28 is ?xed; the
claim as new therein and desireto secure by.
other end of the rod being operatively attached. to
<
.
the braking mechanism 1. The forward .end of 50 Letters Patent is‘: - > .
1. In a tractor having -a main frame, traction
the valve rod I36 connects rigidly with the brake
units at oppositesides of the main frame forits
rod I05 as a continuation thereof, and‘ this, in
turn, has a pivotal connection at its forward end ' support, a prime. mover mounted by the main
frame, driving connections between the prime
'
I "
A requirement for the intended operation of 65 mover and the traction units, each connection
including a steering clutch and ‘brake, individual
the brakes is ‘that the holding tension of "the
braking means applied directly to the traction
coiled spring I31 be less than the releasing ten
with the foot pedal 31.
units, and a brake applying ‘means common to
sion of the steering clutch mechanism 0 so'thatv
' when ‘the foot pedal is depressed, the valve I35
I the steering clutch brake and traction unit brak
will be moved‘to its open position prior to any 60 ing means at the‘same side of the main frame
and operable .to effect their energization in se
actuation of the transmission brake 9. The un.-.
seating of valve I35 provides for communication
of the vacuum through the valve housing to the
,
quence.
2. A tractor- of the character described com
prising a main frame, swing frames supporting
shown, effects the application of braking force 65 the main frame ‘at opposite sides thereof and
adapted for independent oscillation, ground
vto the front wheel of the unit. Then, by a con
tinued forward actuation of the foot pedal, suin
‘wheels mounted‘ by each swing frame, a prime
' cient to take up all the lost motion ail'orded in
mover mounted by the main frame having sepa
the spring I31, finally results in the functional
rate‘driving connections with the ground wheels
operation of the braking facilities of the steering 70 of different swing frames; each connection in
clutch mechanism 3. The rod I23 might well
cluding a steering clutch and brake, wheel brak
have a limited sliding connection with lever I
ing means applied directly to the ground wheels
so that its braking action becomes effective only
of each swing frame, an energizing means there
after the full effect of the vacuum brake has
for on the corresponding swing frame and a
been used.
‘
brake control means on the main frame common
booster drum, and this, through the connections
2,862,698
to the steering clutch brake and wheel braking
means at the same‘side of the tractor.
'
3; A tractor of the character described com
prising'a main frame, swing frames supporting
the main frame at opposite sides thereof and
mounted for independent oscillation, ground
wheels mounted by each swing frame, a prime
'
'
5
yieldable, lost motion Joint therein, and where
- in means is operable incident to the initial brake
applying movement of the brake rod, for effect
ing an application of braking force to the ground
5 wheels, and other means is operable, after lost
motion in the joint has been overcome by the
initial braking action, to e?ect the application
mover mounted by the main frame having sepa
of the steering brake mechanism.
_
rate connections with the ground wheels of the
5. _In a tractor having traction units at oppo
di?erent swing frame; each driving connection 10 site sides thereof, a prime mover with driving
including steering brake mechanism, braking
connections extended to the traction units and
means applied directly to the ground wheels at
including a steering clutch and brake mecha
' opposite sides of the tractor, and a manually
nism in each driving connection; a braking
means. for each traction unit independent of
controlled brake applying means, common to
the steering brake mechanism and wheel brak 15 the steering clutch brake and including a ?uid
- pressure medium booster connected to actuate
ing means at the same side of the tractor, mov
able through'an initial interval for actuation of
the braking means, a source of ?uid pressure
the wheel braking means and through an addi
medium having connection with the booster, a
tional interval to actuate the steering brake
control valve in the connection and a manually
20 operable brake control means movable through
mechanism.
4. A tractor as recited in claim 3 wherein
an initial interval. to open the valve to apply
means is associated with each of the steering
the pressure medium to the booster for actuating
brake mechanisms to yieldingly resist its appli
the unit brake and movable through an addi
tional interval to apply the corresponding steer
cation, and wherein said brake applying means
I
includes a brake rod connection with the steer 25 ing clutch brake.
. GEORGE S. 'ALLIN.
ing brake mechanism; said brake rod having a
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